Formerly reliable social conservative wedge issues like gay marriage were overshadowed by the economy.

McCain hired the same political hitmen (e.g. Tucker Eskew) that Bush used to slime him in 2000. The result made McCain look like someone who was willing to compromise his own dignity to win.

Bloggers posting video of ugly behavior at McCain rallies (e.g. Crazy McCain Lady, racism) did not cast the campaign in a good light.

McCain's fundraising never took off.

McCain often wasted time stumping in states he either had locked up (Tennessee), or didn't have a chance to win (Iowa, California).

Using blue-collar workers as populist superheroes (e.g. Tito The Laborer, Joe The Plumber) soon became a public joke, especially when Joe Werzelbacher—who wasn't even a licensed plumber—began fielding questions at McCain events about US-Israeli policy.